The aim of the proposed project is to produce affinity-purified, highly specific antibodies with which to detect and measure the highly potent opioid peptide dynorphin. Since dynorphine contains the smaller opioid peptide leucine-enkephalin within its structure, antisera directed to one may yield ambiguous results concerning the presence of the other. Yet a major problem is to sort out the various systems of opioid peptides. At present it appears that dynorphin represents a neuropeptide entirely unrelated to the enkephalins or to beta-endorphin. The availability of pure and specific antibodies of the kinds proposed for development here will facilitate progress in immunoassay, immunohistochemical localization, and isolation of dynorphin peptides.